http://codegolf.stackexchange.com/questions/245/print-a-random-maze

random-maze.rb

class Map
  def initialize width, height
    @values = Array.new(width){ Array.new(height){ nil } }
  end

  def [](x, y)
    @values[x][y]
  end

  def []=(x, y, value)
    @values[x][y] = value
  end
end

class Maze
  def initialize config={}
    @width           = config[:width]           || 100
    @height          = config[:height]          || 100
    @num_runners     = config[:num_runners]     || 5
    @dead_end_chance = config[:dead_end_chance] || 0.05

    case Random.rand
    when 0..0.25
      @start_index = [0, Random.rand(@height)]
    when 0.25..0.5
      @start_index = [@width - 1, Random.rand(@height)]
    when 0.5..0.75
      @start_index = [Random.rand(@width), 0]
    when 0.75..1
      @start_index = [Random.rand(@width), @height - 1]
    end
  end

  def generate
    @map = Map.new(@width, @height)
    @map[*@start_index] = :empty
    runners = [@start_index]
    while (! runners.empty?)
      current = runners.shift
      nixt = self.choose_direction current
      while runners.length < @num_runners && nixt != nil
#        if Random.rand < @dead_end_chance
#          @map[*nixt] = :wall
#        else
          @map[*nixt] = :empty
          runners << nixt
#        end
        nixt = self.choose_direction current
      end
      self.neighbours(current).each do |point|
        @map[*point] = :wall
      end
    end
    @map[*current] = :treasure
  end

  def choose_direction point
    n = self.neighbours point
    n.empty? ? nil : n[Random.rand(n.length)]
  end

  def all_neighbours point
    [
      [point[0] - 1, point[1]    ],
      [point[0] - 1, point[1] + 1],
      [point[0] - 1, point[1] - 1],
      [point[0] + 1, point[1]    ],
      [point[0] + 1, point[1] + 1],
      [point[0] + 1, point[1] - 1],
      [point[0]    , point[1] - 1],
      [point[0]    , point[1] + 1]
    ].select {|point| point[0] > 0 and point[0] < @width and point[1] > 0 and point[1] < @height }
  end

  def horiz_neighbours point
    [
      [point[0] - 1, point[1]    ],
      [point[0] + 1, point[1]    ],
    ].select {|point| point[0] > 0 and point[0] < @width }
  end

  def four_neighbours point
    [
      [point[0] - 1, point[1]    ],
      [point[0] + 1, point[1]    ],
      [point[0]    , point[1] - 1],
      [point[0]    , point[1] + 1]
    ].select {|point| point[0] > 0 and point[0] < @width and point[1] > 0 and point[1] < @height }
  end


  def neighbours point
    [
      [point[0] - 1, point[1]],
      [point[0] + 1, point[1]],
      [point[0], point[1] - 1],
      [point[0], point[1] + 1]
    ].select {|point| point[0] > 1 and point[0] < @width - 1 and point[1] > 1 and point[1] < @height - 1 and @map[*point] == nil }
  end

  def determine_wall_char x, y
    if all_neighbours([x,y]).map{|p|@map[*p]}&[:empty, :treasure] == []
      ' '
    else
      case (four_neighbours([x,y]).map{|p|@map[*p]}.select{|y|[:empty,:treasure].include? y}).length
      when 0, 3, 4
        '+'
      when 1
        case (horiz_neighbours([x,y]).map{|p|@map[*p]}.select{|y|[:empty,:treasure].include? y}).length
        when 0
          '-'
        when 1
          '|'
        end
      when 2
        case (horiz_neighbours([x,y]).map{|p|@map[*p]}.select{|y|[:empty,:treasure].include? y}).length
        when 0
          '-'
        when 1
          '+'
        when 2
          '|'
        end
      else
        '?'
      end
    end
  end

  def determine_char x, y
    case @map[x,y]
    when :treasure
      '#'
    when :empty
      ' '
    when :wall, nil
      determine_wall_char x, y
    else
      '?'
    end
  end

  def draw
    @height.times do |y|
      @width.times do |x|
        print determine_char x, y
      end
      puts
    end
  end
end

if $0 == __FILE__
  if ARGV.length != 2
    puts "Usage: ruby #{$0} <width> <height>"
    exit -1
  end
  maze = Maze.new :width => ARGV[0].to_i, :height => ARGV[1].to_i
  maze.generate
  maze.draw
end